Choose a novel that is two grade levels above your current reading level at the beginning of each week. Make it a personal goal to complete this novel by the end of the week. Excellent authors for adults seeking to increase their reading and spelling skills include Charles Dickens, Thomas Hardy and Angela Hunt.
Note any words with which you're unfamiliar in a note pad and look up their pronunciation and definition in the dictionary. Remember that vocabulary does you little good simply remaining in a book--it must be used and practiced.
Avoid using the spell-check function on anything you write on a computer until you're finished writing. Jot down every misspelled word in a notepad and practice the correct spelling regularly, by either writing it out 10 times or spelling it aloud.
Memorize grammatical rules to improve your spelling of new words. A good example is, "I before E, except after C. Or when sounding like A, as in neighbour, or weigh."